1. Field of the Invention
The invention relates to a heat dissipation device.
An electronic device such as a desktop computer requires a heat dissipation device such as a fan.
2. Brief Discussion of the Related Art
A conventional heat dissipation device mainly employs two control methods, a temperature control method and a pulse width modulation control method, shown in FIGS. 1a and 1b respectively. In FIG. 1a, a temperature sensor 20 is connected to a fan 10. The temperature sensor 20 detects the temperature variation of a heat source, such as an electronic element (not shown) and transmits a signal to change the speed of the fan 10. Reference numbers 12 and 14 represent positive and negative voltage output from a power supply to the fan 10. Reference number 16 is a squared-wave signal FG indicating speed of the fan 10 and the signal transmitted to the electronic device (not shown) serving as a feedback signal.
In FIG. 1b, the speed of the fan 10′ is controlled by a pulse width modulation signal (referred to as a PWM signal herein) 40 from the electronic device. The output of the PWM signal 40 for fan speed control is based on various requirements, for example, a sudden rise in temperature of electronic elements. Reference numbers 12′ and 14′ represent positive and negative voltage from a power supply to the fan 10′. Reference number 16′ is a squared-wave signal FG indicating speed of the fan 10′ and transmitted to the electronic device (not shown) serving as a feedback signal.
Either the fan 10 or the fan 10′ is controlled by a unitary control method. This, however, limits the applicability of the fan to various electronic devices using different control methods.
Thus, a fan provided with several control modes is required for various applications.